A RECOMBINANT ANTIGEN FROM THE HEARTWATER AGENT (COWDRIA-RUMINATIUM) REACTIVE WITH ANTIBODIES IN SOME SOUTHEASTERN UNITED-STATES WHITE-TAILED DEER (ODOCOILEUS-VIRGINIANUS), BUT NOT CATTLE, SERA

Recombinant baculovirus techniques were used to express the 260 amino acid carboxyterminal portion of the 32 kilodalton (kDa) major antigeni c protein (MAP 1) of Cowdria ruminantium, the heartwater agent, as a f usion protein. The recombinant MAP 1 was fused to an aminoterminal ind ependently antigenic octapeptide sequence (FLAG(R) peptide). Recombina nt MAP 1 was used as an immunoblotting antigen to evaluate numerous re ference antisera against organisms of the tribe Ehrlichieae. Monoclona l and polyclonal C. ruminantium antibodies, monoclonal anti-FLAG(R) as cites, and antisera to Ehrlichia canis and Ehrlichia chaffeensis react ed with this antigen. Twelve of 79 sera collected 1980 to 1992 from so utheastern U.S. white-tailed deer (Odocoileus virginianus) were also u nexpectedly immunoblot-positive to MAP 1. These 12 deer sera had, as a group, significantly (P < 0.01) greater anti-E. chaffeensis titers (p reviously determined) than the sera from MAP 1 immunoblot-negative dee r living in the same areas. None of the 262 sera from cattle living in tile same areas were immunoblot-positive to MAP 1. All of an addition al 50 cervine sera from Michigan (USA), 72 bovine sera from northern U .S. cattle, and 72 sera from Puerto Rican cattle were also immunoblot- negative to MAP 1. Sera from African sheep which were falsely seroposi tive to authentic MAP 1 were also immunoblot-positive to the recombina nt MAP 1. Unidentified Ehrlichia spp, capable of serologic crossreacti vity with the heartwater agent appear to be present in some southeaste rn U.S. white-tailed deer but not cattle. These or related Ehrlichia s pp. may also be found elsewhere in the world in non-cervine species.